I have three versions of Postgres (8.4, 9.0, 9.1) running on my Ubuntu box. Each version is configured to listen on a different port. When I reboot the machine, only the 9.0 version starts automatically.

I can start the other versions manually via "sudo /etc/init.d/postgresql start 9.1", but I can't figure out where the configuration is that passes the parameter into the script when the server is booting.